Swiss author Erich von Däniken, whose books offered up extraterrestrial explanations for humanity’s mysteries, has died.

Swiss author Erich von Däniken has died at the age of 90, his office says.

Known for his theories about extraterrestrials, the writer died on Saturday after a short hospital stay in Unterseen near the Swiss capital Bern, his office said.

His family later confirmed the news of his death.

The bestselling author wrote dozens of books about himself and what he believed to be traces of aliens on earth.

Among other things, he asserted the theory that the pyramids in Egypt were built with the help of aliens.

On his YouTube channel, the trained chef lectured in many talks about visitors from space in ancient times who were perceived by humans at the time as gods.

He also discussed questions such as whether extraterrestrials have the same sexual organs as humans.

In 1968, during the early years of the space age, his first book titled Chariots of the Gods? Unsolved Mysteries of the Past was published.

In it, he interpreted humanity’s mysteries as evidence of visits from extraterrestrials.

For him, the biblical account of the prophet Ezekiel about the appearance of God on Mount Sinai was nothing other than the landing of a spaceship.

The book fuelled a growing interest in unexplained phenomena at a time when thanks to conventional science man was about to take its first steps on the moon.

Chariots of the Gods was followed by more than two dozen similar books that sold 60 million copies in 32 languages.

Von Däniken was self-taught.

He had worked as a chef, waiter, bartender and hotelier.

For decades, he immersed himself in reports and books, and undertook hundreds of often adventurous journeys to search for and document the alleged traces of extraterrestrials on earth.

In 1991 von Däniken gained the damning accolade of being the first recipient of the “Ig Nobel” prize for literature – for raising the public awareness of science through questionable experiments or claims.

Even when confronted with fabricated evidence in a UK television documentary – supposedly ancient pots were shown to be almost new – von Däniken insisted that, minor discrepancies aside, his theories were essentially sound.

–with AP